Photon energy delivered to the retina from intraocular fiberoptic instruments during ophthalmic surgical procedures can damage the retina. Retinal damage occasioned by such photon energy is known colloquially in the ophthalmic surgical art as "light toxicity". As a result, concerns have arisen over the amount of photon energy being delivered to the retina during a normal surgical procedure. For example, wavelengths from 400 nm to 700 nm are considered to be the safest for purposes of ophthalmic surgery.
However, even at these wavelengths, retinal damage can occur if retinal exposure the photon energy is prolonged. In this regard, exposure of the retina to light emanating from intraocular fiberoptics during retinal surgery has, in so me cases, resulted in pathologic retinal lesions, some of which have been associated with vision loss. Fiberoptic illumination of the retina, however, remains an essential component of vitreo retinal surgery in order for the surgeon to visualize the tissues undergoing the surgical procedure.
Although the use of visible light within the eye during ophthalmic surgery cannot be eliminated, the desire has been to reduce the amount of photon energy being delivered to the retina during a procedure. For example, light sources that have little of the most harmful wavelengths--i.e., light sources which emit little or no photon energy at wavelengths other than between 400-700 nm--have been employed. However, as noted previously, retinal damage can ensue if exposure is prolonged even at these relatively "safe" wavelengths. Furthermore, filters have also been placed in the light path of the light source so as to block the less save wavelengths. Also, attempts have been made to diffuse the light over larger areas.
Conventional fiberoptic illuminators used to transmit photon energy during ophthalmic surgery are typically formed of polymethylmethacrylate (PMMA) having a nominal numeral aperture (NA) of about 0.66. Most of the energy from these conventional PMMA fiberoptic illuminators is within a 60.degree. cone of light. Some special use fiberoptic lights use glass fibers that have similar optical properties. These conventional illuminators receive their light energy from a standard light source with matching optics allowing for good collection of the energy into the fiber. The fiberoptics are usually of an extended length (e.g., typically about six (6) feet in length) to allow the light emitting end to be used within the surgical field while the light source is maintained in a remote location. The fiberoptics are thus typically draped from the source to the operating field. Since several fiberoptic lights can be in use simultaneously during an operation, the fiberoptics tend to form a tangle of cables running onto the operating field, thereby providing practical complications.
Furthermore, during surgery, there exist the competing demands of providing the surgeon with adequate light to illuminate the surgical field, while at the same time permit relatively instantaneous adjustment of the illumination when desired to thereby reduce the photon energy delivered during periods when full illumination is not needed for the procedure. The surgeon can request that an assistant adjust the intensity of the light at the remotely positioned light source during portions of the surgery when this is feasible or can direct the light away from the most critical portion of the retina (the macula) during pauses in surgery. However, the former technique is problematic since surgical assistants are usually tasked with other responsibilities and thus may not be available to instantaneously adjust the light intensity at the surgeon's request. And, the latter technique may not always be available to the surgeon since the surgeon's hands may be occupied physically with another aspect of the surgical procedure which prevents redirection of the light.
Thus, as can be appreciated from the discussion above, improvements to surgical lights have been needed. It is towards providing such improvements that the present invention is directed.
Broadly, the present invention is embodied in hand-held surgical light assemblies having a light source, and a handpiece which is adapted to be grasped and manipulated by a user. The handpiece has a light guide with a proximal end optically connected to the light source, and a distal end which projects outwardly from said handpiece so as to direct light guided thereby onto a field of view determined by manipulation of the handpiece by the user. The handpiece includes a switch assembly which is operatively coupled to the light source to allow user selection between at least two different light intensities (e.g., essentially on/off) discharged by said light guide onto the field of view.
In preferred forms, the switch assembly includes an electrically conductive inner core and an electrically conductive outer tubular elastomeric member concentrically positioned in surrounding, but spaced relationship, with the inner base. When contact between the inner base and the outer elastomeric member is made, switch circuitry changes the visible light intensity of the visible light generated by the light source, e.g., by either directly modulating the current to the lamp itself, or by providing an electrically operable shutter assembly which masks the light generated by the light source. The former embodiment is especially well suited for surgical lights which are self-contained (i.e., have the light sources contained in the handpiece), while the latter is especially well suited for surgical lights which have remotely positioned light sources.
These, and other, aspects and advantages will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.